Return counts for collection update and remove commands

In order to support optimistic locking the counts from the MongoDB
update and remove commands need to be returned to the application code
so that the update/remove can be verified they took place and action
taken if they did not (like throwing a 409 Error).

For consistency make LocalCollection return counts also.
Merge remote-tracking branch 'meteor/devel' into return-counts-for-update-remove
Merge branch 'return-counts-for-update-remove' of github.com:jacott/meteor into jacott-return-counts-for-update-remove

Conflicts:
	packages/minimongo/minimongo.js
	packages/mongo-livedata/mongo_driver.js
Merge branch 'jacott-return-counts-for-update-remove' into mongo-upsert

Conflicts:
	packages/mongo-livedata/collection.js
Return { numberAffected: x } from updates and removes.